WO2013187211A1 - Negative electrode material for lithium ion secondary batteries, negative electrode for lithium ion secondary batteries, lithium ion secondary battery; method for producing negative electrode material for lithium ion secondary batteries, and method for producing negative electrode for lithium ion secondary batteries - Google Patents

Negative electrode material for lithium ion secondary batteries, negative electrode for lithium ion secondary batteries, lithium ion secondary battery; method for producing negative electrode material for lithium ion secondary batteries, and method for producing negative electrode for lithium ion secondary batteries Download PDF

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WO2013187211A1
WO2013187211A1 PCT/JP2013/064430 JP2013064430W WO2013187211A1 WO 2013187211 A1 WO2013187211 A1 WO 2013187211A1 JP 2013064430 W JP2013064430 W JP 2013064430W WO 2013187211 A1 WO2013187211 A1 WO 2013187211A1
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negative electrode
ion secondary
lithium ion
secondary battery
active material
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PCT/JP2013/064430
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French (fr)
Japanese (ja)
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博史 春名
真人 水谷
登志雄 阿部
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株式会社 日立製作所
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to a negative electrode material for a lithium ion secondary battery, a negative electrode for a lithium ion secondary battery, a lithium ion secondary battery, and a method for producing them.
  • Patent Document 1 describes that a negative electrode active material is treated with boric acid to form a boron-derived film to improve the high-temperature storage characteristics of the battery.
  • Patent Document 2 describes that an additive containing boron is added to the electrolytic solution to improve the cycle characteristics of the battery.
  • Patent Document 1 It is also possible to improve the high-temperature storage characteristics of a battery by forming a film having a BO bond and a film containing lithium on the negative electrode described in Patent Document 1.
  • the method of Patent Document 1 describes that a film containing a compound having a B—O bond is formed by treating an electrode with a boric acid solution.
  • a compound having a B—O bond remains on the surface of the negative electrode, and it is estimated that the compound dissolves in the electrolytic solution, and the battery characteristics may be deteriorated due to a decrease in physical properties of the positive electrode and the electrolytic solution itself.
  • a boron-containing additive when a boron-containing additive is used in the electrolytic solution, the charge is consumed due to the decomposition of the additive, which may cause a decrease in the initial capacity of the battery.
  • Patent Document 2 it is not sufficient to suppress the deterioration with time with the high capacity of batteries in recent years.
  • the object of the present invention is to suppress a decrease in battery capacity after a storage test and to improve battery life characteristics.
  • FIG. 1 is a diagram schematically showing the internal structure of a battery according to an embodiment of the present invention.
  • a battery 1 according to an embodiment of the present invention shown in FIG. 1 includes a positive electrode 10, a separator 11, a negative electrode 12, a battery can 13, a positive electrode current collecting tab 14, a negative electrode current collecting tab 15, an inner lid 16, an internal pressure release valve 17, It comprises a gasket 18, a positive temperature coefficient (PTC) resistance element 19, a battery lid 20, and an axis 21.
  • the battery lid 20 is an integrated part including the inner lid 16, the internal pressure release valve 17, the gasket 18, and the resistance element 19.
  • a positive electrode 10, a separator 11, and a negative electrode 12 are wound around the shaft core 21.
  • the separator 11 is inserted between the positive electrode 10 and the negative electrode 12, and the electrode group wound around the shaft core 21 is produced.
  • the shaft core 21 any known one can be used as long as it can support the positive electrode 10, the separator 11, and the negative electrode 12.
  • the electrode group is formed by stacking strip-shaped electrodes, or the positive electrode 10 and the negative electrode 12 are wound into an arbitrary shape such as a flat shape, or the separator 11 has a bag shape.
  • the positive electrode 10 and the negative electrode 12 can be housed in this, and these can be sequentially stacked to form a multilayer structure.
  • the shape of the battery can 13 may be selected from shapes such as a cylindrical shape, a flat oval shape, a flat oval shape, and a square shape according to the shape of the electrode group.
  • the material of the battery can 13 is selected from materials that are corrosion resistant to non-aqueous electrolytes, such as aluminum, stainless steel, and nickel-plated steel. Further, when the battery can 13 is electrically connected to the positive electrode 10 or the negative electrode 12, the material is not deteriorated due to corrosion of the battery can 13 or alloying with lithium ions in the portion in contact with the nonaqueous electrolyte. Thus, the material of the battery can 13 is selected.
  • Stainless steel is resistant to corrosion because a passive film is formed on the surface, and since it is steel, it has high strength and can withstand the increase in the internal pressure of gas vaporized from the electrolyte in the battery can 13 or the like.
  • Aluminum is characterized by its high energy density per weight due to its light weight.
  • the electrode group is housed in the battery can 13, the negative electrode current collecting tab 15 is connected to the inner wall of the battery can 13, and the positive electrode current collecting tab 14 is connected to the bottom surface of the battery lid 20.
  • the electrolyte is injected into the battery can 13 before the battery is sealed.
  • a method for injecting the electrolyte there are a method of adding directly to the electrode group in a state where the battery cover 20 is released, or a method of adding from an injection port installed in the battery cover 20.
  • a positive current collecting tab 14 and a negative current collecting tab 15 for drawing current are formed on each of the positive electrode 10 and the negative electrode 12 by spot welding or ultrasonic welding.
  • the positive electrode current collecting tab 14 and the negative electrode current collecting tab 15 are made of a metal foil of the same material as the positive electrode current collector and the negative electrode current collector plate each having a rectangular shape, and for taking out current from the positive electrode 10 and the negative electrode 12. It is a member to install.
  • the present invention can be applied to a lithium secondary battery for a mobile object such as an automobile, and since these are required to pass a large current, a plurality of lithium secondary batteries for a mobile object such as an automobile are used. It is necessary to provide a tab.
  • the battery lid 20 is brought into close contact with the battery can 13 and the whole battery is sealed. If there is an electrolyte inlet, seal it as well.
  • a method for sealing the battery there are known techniques such as welding and caulking.
  • the battery lid 20 is provided with a relief valve that is opened when the pressure inside the battery rises and releases the pressure inside the battery.
  • the lithium ion secondary battery according to an embodiment of the present invention can be manufactured by, for example, disposing the following negative electrode and positive electrode facing each other via a separator and injecting an electrolyte.
  • the structure of the lithium ion battery according to an embodiment of the present invention is not particularly limited.
  • the positive electrode and the negative electrode and the separator separating them are wound into a wound electrode group, or the positive electrode, the negative electrode, and the separator are combined.
  • a stacked electrode group can be formed by stacking.
  • a boron-containing compound reacts with a surface functional group such as a C ⁇ O, C—OH, and —COOH bond in which a carbon edge portion as a negative electrode active material exists.
  • the negative electrode active material can be immobilized on the surface, that is, the negative electrode active material and the boron-containing compound can be covalently bonded.
  • the surface functional group present on the surface of the negative electrode active material reacts irreversibly with the electrolytic solution in a battery reaction, thereby forming a surface film called an SEI film.
  • SEI film surface film
  • the generation of the surface coating consumes electric charge and contributes to a decrease in battery capacity.
  • the lifetime can be extended by forming a film that suppresses the reaction with the electrolyte over time.
  • a boron compound having a BO bond is immobilized on a part or all of the surface of the negative electrode active material, thereby suppressing deterioration with time of the battery. , Found to improve life.
  • immobilizing the compound on part or all of the surface of the negative electrode active material it is possible to reduce the concern of elution into the electrolyte and to suppress the deterioration of the characteristics of the positive electrode, contributing to the improvement of battery characteristics. it is conceivable that.
  • the raw material of the negative electrode active material in one embodiment of the present invention can be used as long as it has a surface functional group. That is, if a material is analyzed by X-ray photoelectron spectroscopy or the like, any material that can detect a peak derived from an O atom can be used. Specifically, graphitized materials obtained from natural graphite, petroleum coke, coal pitch coke, etc., processed at a high temperature of 2500 ° C.
  • the carbon material carrying a metal include a metal or an alloy selected from lithium, aluminum, tin, silicon, indium, gallium, and magnesium.
  • the said metal or metal oxide can be utilized as a negative electrode active material. Of these negative electrode active material candidates, one kind can be used alone, or two or more kinds can be used in combination.
  • MB (OR) is produced by reacting R-OM produced by the reaction of monovalent or divalent alkali metal (M) with alcohol (R—OH) and alkyl borate (B— (OR) 3 ). A compound containing 4 is obtained.
  • M is a monovalent alkali metal, it can be isolated as an intermediate in the chemical reaction formula.
  • M is a divalent alkali metal, such as Ca ion, it is considered that an association pair is formed to match the charge balance, but solvates in the solution.
  • R is an organic group.
  • the hydrogen of R may be substituted with a halogen element such as fluorine, chlorine or bromine.
  • a branched alkyl group such as an isopropyl group may also be used.
  • the obtained MB (OR) 4 and the surface functional group of the negative electrode active material are stirred and reacted in a more polar solvent such as alcohol or acetonitrile or dimethyl sulfoxide, thereby containing boron and an alkali metal.
  • a negative electrode material in which the coated film agent is formed on the surface of the negative electrode active material can be obtained. From the viewpoint of facilitating solvent removal after the reaction, it is desirable to use a solvent having a lower boiling point.
  • the details of the formation mechanism and reaction product on the surface of the negative electrode active material are unknown, but when a carbon-based negative electrode active material is used, Li—B (—OCH 3 ) 2 -C 2 (derived from a functional group present on the surface of the active material).
  • a material having —OH or —COOH is considered suitable.
  • MB as the compound (O-R) 4 only may be but, MB (O-R) may contain 4 else.
  • R-OM, B- (OR) 3 , and MB (O—R) 4 are substances that easily react with moisture, so that they can be reacted in an inert atmosphere such as Ar or N 2. Although it is desirable, even in the atmosphere, the reaction yield is only slightly reduced, and it is possible to maintain the yield by selecting process conditions such as subsequent stirring time with the negative electrode active material and heating. is there.
  • boron compounds include trimethyl borate (B (OCH 3 ) 3 ), triethyl borate (B (OCH 2 CH 3 ) 3 ), and tripropyl borate (B (OCH 2 CH 2 CH 3 ) 3 ).
  • alkyl borate From the viewpoint of low boiling point and easy removal, it is desirable to use trimethyl borate having a short alkyl group.
  • the above negative electrode material is used, mixed with a binder such as carboxymethyl cellulose and a styrene butadiene copolymer, and applied and pressed to produce an electrode.
  • the thickness of the negative electrode mixture layer is preferably 50 to 200 ⁇ m.
  • the battery capacity can be increased by fixing the coating agent to the negative electrode active material in advance before forming the negative electrode 12.
  • the total amount of the dispersing agent / binder such as carboxymethyl cellulose and styrene butadiene copolymer is about 3 wt%.
  • the binder component increases, the internal resistance value increases and the battery capacity decreases.
  • preparation of electrode peeling may become difficult, storage of a battery, and the fall of a cycle life may be caused.
  • the positive electrode 10 includes a positive electrode active material, a conductive agent, a binder, and a positive electrode current collector.
  • a positive electrode active material that reversibly absorbs and releases lithium, lithium cobaltate (LiCoO 2 ), lithium nickelate (LiNiO 2 ), etc.
  • the above positive electrode active material is mixed with a carbon material powder conductive agent and a binder such as polyvinylidene fluoride (PVDF) to prepare a slurry.
  • the mixing ratio of the conductive agent to the positive electrode active material is preferably 5 to 20 wt%.
  • the mixture is sufficiently kneaded using a mixer equipped with stirring means such as a rotary blade so that the powder particles of the positive electrode active material are uniformly dispersed in the slurry.
  • the sufficiently mixed slurry is applied on both sides onto a positive electrode current collector made of aluminum foil having a thickness of 15 to 25 ⁇ m, for example, by a roll transfer type coating machine. After coating on both sides, a positive electrode 10 was obtained by press drying.
  • the thickness of the positive electrode mixture layer applied on the positive electrode current collector is preferably 50 to 250 ⁇ m.
  • non-aqueous solvent examples include ethylene carbonate, propylene carbonate, gamma butyrolactone, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate.
  • solvents may be used alone or in combination of two or more.
  • Lithium salt such as LiPF 6 , LiBF 4 , LiClO 4 , LiAsF 6 , LiCF 3 SO 2 , Li (CF 3 SO 2 ) 2 N, Li (C 2 F 5 SO 2 ) N, etc. should be used as the lithium salt. Can do. These lithium salts may be used alone or in combination of two or more.
  • As the electrolytic solution it is desirable to use a solution of LiPF 6 or LiBF 4 as an electrolyte in a solvent such as ethylene carbonate, propylene carbonate, or dimethyl carbonate.
  • the electrolyte concentration is preferably between 0.6 and 1.5 mol / L.
  • vinylene carbonate a compound having a carboxylic acid anhydride group, a compound having a sulfur element such as propane sultone, or a compound having boron as a third component other than a solvent and a solute in the electrolytic solution.
  • a compound having a carboxylic acid anhydride group a compound having a sulfur element such as propane sultone
  • a compound having boron a third component other than a solvent and a solute in the electrolytic solution.
  • two or more compounds in addition to the solvent and solute is not only to suppress reductive decomposition on the surface of the negative electrode active material, but also to suppress Mn elution from the positive electrode active material, improve the ionic conductivity of the electrolyte, make the electrolyte non-flammable, flame retardant, etc. Select according to purpose.
  • a coating agent that forms a coating on the surface of a negative electrode active material such as vinylene carbonate / propane sultone
  • an overcharge prevention additive such as cyclohexylbenzene, phosphoric acid type or halogen substitution
  • Additives that impart flame retardancy, self-extinguishing additives, electrode / separator wettability improving additives, and the like may be added according to their respective purposes.
  • a separator 11 is used for the purpose of preventing a short circuit due to direct contact between the positive electrode 10 and the negative electrode 12, and the separator 11 includes a microporous polymer film such as polyethylene, polypropylene, and aramid resin, and alumina particles and the like on this polymer film.
  • a film having a surface coated with a heat-resistant substance can be used.
  • the positive electrode active material Li 1.02 Mn 1.98 Al 0.02 O 4 having an average particle diameter of 10 ⁇ m and a specific surface area of 1.5 m 2 / g was used.
  • a mixture of 9: 2 of massive graphite and acetylene black mixed with 85% by weight of the positive electrode active material is used as a conductive agent, and the conductive agent is dispersed in an NMP solution that has been previously adjusted to 5% by weight PVDF as a binder. did.
  • the mixing ratio of the positive electrode active material, the conductive agent, and PVDF was 85: 10: 5 by weight.
  • the slurry was applied as uniformly and evenly as possible to an aluminum foil (positive electrode current collector) having a thickness of 20 ⁇ m. After the application, the film was dried at a temperature of 80 ° C., and applied and dried on both sides of the aluminum foil in the same procedure. Thereafter, it was compression-molded by a roll press machine, cut to a coating width of 5.4 cm and a coating length of 50 cm, and an aluminum foil lead piece for taking out the current was welded to produce the positive electrode 10.
  • the negative electrode active material natural graphite having an interplanar spacing of 0.368 nm, an average particle diameter of 20 ⁇ m, and a specific surface area of 5 m 2 / g obtained by X-ray diffraction measurement was used.
  • methanol alkoxide formed by reaction of lithium metal and methanol was obtained, and then reacted with trimethyl borate to synthesize LiB (O—CH 3 ) 4 .
  • LiB (O—CH 3 ) 4 By reacting the obtained LiB (O—CH 3 ) 4 with the surface functional group of the negative electrode active material, a negative electrode material containing boron and an alkali metal was obtained.
  • the negative electrode material and an aqueous dispersion of carboxymethyl cellulose were sufficiently mixed, and the aqueous dispersion of styrene-butadiene copolymer was dispersed to obtain a negative electrode slurry.
  • the mixing ratio of the negative electrode material, carboxymethyl cellulose, and styrene butadiene was 98: 1: 1 by weight.
  • This slurry was applied substantially uniformly to a rolled copper foil (negative electrode current collector) having a thickness of 10 ⁇ m.
  • the coating and drying were performed on both sides of the rolled copper foil in the same procedure as the positive electrode 10. Thereafter, it was compression-molded by a roll press machine, cut so as to have a coating width of 5.6 cm and a coating length of 54 cm, and a lead piece made of copper foil was welded to prepare the negative electrode 12.
  • a cylindrical battery 1 shown in FIG. 1 was produced using the produced positive electrode 10 and negative electrode 12.
  • a positive electrode 1 and a negative electrode 2 shown in FIG. 1 are formed, and a positive electrode lead 7 and a negative electrode lead 5 of a tab portion for drawing out current are formed by ultrasonic welding.
  • the positive electrode lead 7 and the negative electrode lead 5 in the tab portion are made of metal foils of the same material as the current collector having a rectangular shape, and are members installed to take out current from the electrodes.
  • a separator 11, which is a polyethylene single layer film, is sandwiched between the tabbed positive electrode 1 and negative electrode 2, and this is rolled into a cylindrical shape (spiral) as shown in FIG.
  • the battery can 13 was housed in a cylindrical container.
  • an electrolytic solution was injected into the battery can 13 and sealed with a gasket.
  • EC ethylene carbonate
  • EMC ethyl methyl carbonate
  • the thus-prepared electrolyte is poured into a battery can 13 through a gasket 18 and a battery lid 20 for sealing, to which a positive electrode terminal is attached, and is sealed by caulking to form a cylindrical shape having a diameter of 18 mm and a length of 650 mm. Battery 1 was obtained.
  • the cylindrical battery 1 manufactured in this way was charged in a constant temperature bath at 25 ° C. with a charging current of 150 mA, a voltage of 4.2 V, and a constant current and a constant voltage of 5 hours, and discharging was performed at a discharging current of 1500 mA and a battery voltage of 3.
  • a constant current was discharged to 0V.
  • This charging / discharging process was defined as one cycle, for a total of 3 cycles.
  • the discharge capacity at the third cycle was defined as 100%, and the ratio with the 1500 mA discharge capacity after the 60-day storage test was calculated. This ratio is defined as a discharge capacity maintenance rate.
  • the storage test was conducted at a voltage of 4.2 V in a constant temperature bath at 50 ° C.
  • the measurement of the battery capacity after 60 days was left in a constant temperature bath at 25 ° C. for 10 hours or more, and the test was started after removing heat.
  • a cylindrical battery was prepared and tested in the same manner as in Example 1 except that triethyl borate was used instead of trimethyl borate as the reactant of the negative electrode active material.
  • Example 1 A cylindrical battery was produced and tested in the same manner as in Example 1 except that solid natural graphite not subjected to boron treatment was used.
  • Comparative Example 2 A cylindrical battery was prepared and tested in the same manner as in Comparative Example 1 except that LiB (O—CH 3 ) 4 was dissolved in the electrolyte at a concentration of 1 wt%.
  • Comparative Example 3 A cylindrical battery was prepared and tested in the same manner as in Comparative Example 1 except that LiB (O—CH 3 ) 4 was dissolved in the electrolyte at a concentration of 2 wt%.
  • Table 1 shows the high temperature storage characteristics after 60 days as a result of each of the battery tests described above.
  • Example 2 As described in Example 2, when triethyl borate was used as a starting material, the capacity after storage after 60 days was improved by 4.3% as compared with Comparative Example 1. It was found that the capacity was improved even when the alkyl bonded to the boric acid group was changed.
  • Example 2 the batteries after the 60-day storage test described in Example 1 and Example 2 were disassembled and the positive electrode / electrolyte was analyzed.
  • the boron-containing material was used as the negative electrode active material because boron element was not detected. By fixing, it is thought that it was able to contribute to the improvement of battery life.
  • the storage characteristics of the battery can be greatly improved by immobilizing a compound containing boron, lithium, carbon, and oxygen on the surface of the negative electrode active material.
  • the battery performance may decrease due to the increase in the viscosity of the electrolytic solution or high concentration dissolution may be difficult. I understood. Therefore, according to the present invention, it is possible to suppress deterioration over time and to significantly improve the life characteristics of the battery as compared with the conventional lithium ion battery using the negative electrode active material.

Abstract

Provided is a lithium secondary battery which is reduced in deterioration over time with respect to the battery performance. A negative electrode material for lithium ion secondary batteries, which contains a negative electrode active material and a coating agent that is immobilized on the negative electrode active material. The coating agent contains boron and an alkali metal element, and the coating agent is immobilized on the negative electrode active material by reacting the coating agent with surface functional groups of the negative electrode active material. The coating agent is exemplified by trimethyl borate and the like. A lithium ion secondary battery which uses the negative electrode material for lithium ion secondary batteries.

Description

リチウムイオン二次電池用負極材、リチウムイオン二次電池用負極、リチウムイオン二次電池、およびそれらの製造方法Negative electrode material for lithium ion secondary battery, negative electrode for lithium ion secondary battery, lithium ion secondary battery, and production method thereof
　本発明は、リチウムイオン二次電池用負極材、リチウムイオン二次電池用負極、リチウムイオン二次電池、およびそれらの製造方法に関するものである。 The present invention relates to a negative electrode material for a lithium ion secondary battery, a negative electrode for a lithium ion secondary battery, a lithium ion secondary battery, and a method for producing them.
　近年の携帯電話や携帯用パソコンなどの移動体通信用電源はますます小型化、高エネルギー密度化が要望されるとともに、深夜電力の貯蔵のみならず、太陽電池や風力発電と組み合わせた電力貯蔵用電源の開発も進んでいる。また、カルフォルニア州規制に代表されるように環境問題から電気自動車や電力を動力の一部に利用したハイブリッド車、ハイブリッド電車の実用化が進んでいる。しかしながら、非水電解液二次電池は、充放電を繰り返すことで、充放電効率の低下を示すため、電池性能の経時劣化が小さいリチウム二次電池が求められている。 In recent years, mobile communication power supplies such as mobile phones and personal computers are increasingly required to be smaller and have a higher energy density, and not only for storing midnight power but also for storing power combined with solar cells and wind power generation. Power supply development is also progressing. In addition, as represented by California regulations, hybrid vehicles and hybrid trains that use electric vehicles and electric power as part of their power have been put into practical use due to environmental problems. However, since the non-aqueous electrolyte secondary battery shows a decrease in charge / discharge efficiency by repeating charge / discharge, a lithium secondary battery with small deterioration of battery performance with time is required.
　特許文献１には、負極活物質をホウ酸処理することにより、ホウ素由来の被膜を形成させ、電池の高温保存特性を向上させることが記載されている。また、特許文献２には、電解液にホウ素を含有する添加剤を添加し、電池のサイクル特性を向上させることが記載されている。 Patent Document 1 describes that a negative electrode active material is treated with boric acid to form a boron-derived film to improve the high-temperature storage characteristics of the battery. Patent Document 2 describes that an additive containing boron is added to the electrolytic solution to improve the cycle characteristics of the battery.
特開２００３－１５１５３９号公報JP 2003-151539 A 特開２０１０－１９２４３０号公報JP 2010-192430 A
　特許文献１に記載の負極にＢ－Ｏ結合を有する被膜とリチウムを含む被膜を形成することでも電池の高温保存特性を向上することは可能である。しかしながら、特許文献１の方法では、電極をホウ酸溶液で処理することで、Ｂ－Ｏ結合を有する化合物を含有する被膜を形成させることが記載されている。この方法では、負極表面にＢ－Ｏ結合を有する化合物が残存しており、電解液に溶解することが推定され、正極および電解液自体の物性低下による電池特性の低下が考えられる。また、特許文献１に記載の方法では、電解液にホウ素含有添加剤を用いると、添加剤の分解により電荷が消費されるので、電池の初期容量低下を招くことが考えられる。 It is also possible to improve the high-temperature storage characteristics of a battery by forming a film having a BO bond and a film containing lithium on the negative electrode described in Patent Document 1. However, the method of Patent Document 1 describes that a film containing a compound having a B—O bond is formed by treating an electrode with a boric acid solution. In this method, a compound having a B—O bond remains on the surface of the negative electrode, and it is estimated that the compound dissolves in the electrolytic solution, and the battery characteristics may be deteriorated due to a decrease in physical properties of the positive electrode and the electrolytic solution itself. Further, in the method described in Patent Document 1, when a boron-containing additive is used in the electrolytic solution, the charge is consumed due to the decomposition of the additive, which may cause a decrease in the initial capacity of the battery.
　特許文献２の技術では、近年の電池の高容量で経時劣化を抑制することは十分ではない。 In the technique of Patent Document 2, it is not sufficient to suppress the deterioration with time with the high capacity of batteries in recent years.
　本発明は、保存試験後の電池容量の低下を抑制し、電池の寿命特性を向上させることを目的とする。 The object of the present invention is to suppress a decrease in battery capacity after a storage test and to improve battery life characteristics.
　上記課題を解決するための本発明の特徴は、例えば以下の通りである。 The features of the present invention for solving the above problems are as follows, for example.
　負極活物質と、負極活物質に固定化された被覆剤と、を有するリチウムイオン二次電池用負極材であって、被覆剤にホウ素およびアルカリ金属元素が含まれるリチウムイオン二次電池用負極材、リチウムイオン二次電池用負極、リチウムイオン二次電池、およびそれらの製造方法。 A negative electrode material for a lithium ion secondary battery having a negative electrode active material and a coating material fixed to the negative electrode active material, the negative electrode material for a lithium ion secondary battery containing boron and an alkali metal element in the coating material , Negative electrode for lithium ion secondary battery, lithium ion secondary battery, and production method thereof.
　本発明により、保存試験後の電池容量の低下を抑制し、電池の寿命特性を向上できる。上記した以外の課題、構成及び効果は以下の実施形態の説明により明らかにされる。 According to the present invention, it is possible to suppress a decrease in battery capacity after a storage test and improve battery life characteristics. Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.
本発明の一実施形態に係る電池の内部構造を模式的に表す図。The figure which represents typically the internal structure of the battery which concerns on one Embodiment of this invention.
　以下、図面等を用いて、本発明の実施形態について説明する。以下の説明は本発明の内容の具体例を示すものであり、本発明がこれらの説明に限定されるものではなく、本明細書に開示される技術的思想の範囲内において当業者による様々な変更および修正が可能である。また、本発明を説明するための全図において、同一の機能を有するものは、同一の符号を付け、その繰り返しの説明は省略する場合がある。 Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following description shows specific examples of the contents of the present invention, and the present invention is not limited to these descriptions. Various modifications by those skilled in the art are within the scope of the technical idea disclosed in this specification. Changes and modifications are possible. In all the drawings for explaining the present invention, components having the same function are denoted by the same reference numerals, and repeated description thereof may be omitted.
　図１は、本発明の一実施形態に係る電池の内部構造を模式的に表す図である。図１に示す本発明の一実施形態に係る電池１は、正極１０、セパレータ１１、負極１２、電池缶１３、正極集電タブ１４、負極集電タブ１５、内蓋１６、内圧開放弁１７、ガスケット１８、正温度係数（Positive temperature coefficient；ＰＴＣ）抵抗素子１９、及び電池蓋２０、軸芯２１から構成される。電池蓋２０は、内蓋１６、内圧開放弁１７、ガスケット１８、及び抵抗素子１９からなる一体化部品である。また、軸芯２１には、正極１０、セパレータ１１及び負極１２が捲回されている。 FIG. 1 is a diagram schematically showing the internal structure of a battery according to an embodiment of the present invention. A battery 1 according to an embodiment of the present invention shown in FIG. 1 includes a positive electrode 10, a separator 11, a negative electrode 12, a battery can 13, a positive electrode current collecting tab 14, a negative electrode current collecting tab 15, an inner lid 16, an internal pressure release valve 17, It comprises a gasket 18, a positive temperature coefficient (PTC) resistance element 19, a battery lid 20, and an axis 21. The battery lid 20 is an integrated part including the inner lid 16, the internal pressure release valve 17, the gasket 18, and the resistance element 19. A positive electrode 10, a separator 11, and a negative electrode 12 are wound around the shaft core 21.
　セパレータ１１を正極１０及び負極１２の間に挿入し、軸芯２１に捲回した電極群を作製する。軸芯２１は、正極１０、セパレータ１１及び負極１２を担持できるものであれば、公知の任意のものを用いることができる。電極群は、図１に示した円筒形状の他に、短冊状電極を積層したもの、又は正極１０と負極１２を扁平状等の任意の形状に捲回したもの、セパレータ１１に袋状のものを用いてこの中に正極１０と負極１２を収納しこれらを順次重ねて多層構造としたもの等、種々の形状にすることができる。電池缶１３の形状は、電極群の形状に合わせ、円筒形、偏平長円形状、扁平楕円形状、角形等の形状を選択してもよい。 The separator 11 is inserted between the positive electrode 10 and the negative electrode 12, and the electrode group wound around the shaft core 21 is produced. As the shaft core 21, any known one can be used as long as it can support the positive electrode 10, the separator 11, and the negative electrode 12. In addition to the cylindrical shape shown in FIG. 1, the electrode group is formed by stacking strip-shaped electrodes, or the positive electrode 10 and the negative electrode 12 are wound into an arbitrary shape such as a flat shape, or the separator 11 has a bag shape. The positive electrode 10 and the negative electrode 12 can be housed in this, and these can be sequentially stacked to form a multilayer structure. The shape of the battery can 13 may be selected from shapes such as a cylindrical shape, a flat oval shape, a flat oval shape, and a square shape according to the shape of the electrode group.
　電池缶１３の材質は、アルミニウム、ステンレス鋼、ニッケルメッキ鋼製等、非水電解質に対し耐食性のある材料から選択される。また、電池缶１３を正極１０又は負極１２に電気的に接続する場合は、非水電解質と接触している部分において、電池缶１３の腐食やリチウムイオンとの合金化による材料の変質が起こらないように、電池缶１３の材料の選定を行う。ステンレス鋼は、表面に不働態皮膜が形成されるので腐食しにくくまた鋼であるので強度が高く電池缶１３内の電解液等が気化したガスの内圧上昇に耐えられる。アルミニウムは、軽量なので重量当りのエネルギー密度が高いという特徴を有する。 The material of the battery can 13 is selected from materials that are corrosion resistant to non-aqueous electrolytes, such as aluminum, stainless steel, and nickel-plated steel. Further, when the battery can 13 is electrically connected to the positive electrode 10 or the negative electrode 12, the material is not deteriorated due to corrosion of the battery can 13 or alloying with lithium ions in the portion in contact with the nonaqueous electrolyte. Thus, the material of the battery can 13 is selected. Stainless steel is resistant to corrosion because a passive film is formed on the surface, and since it is steel, it has high strength and can withstand the increase in the internal pressure of gas vaporized from the electrolyte in the battery can 13 or the like. Aluminum is characterized by its high energy density per weight due to its light weight.
　電池缶１３に電極群を収納し、電池缶１３の内壁に負極集電タブ１５を接続し、電池蓋２０の底面に正極集電タブ１４を接続する。電解液は、電池の密閉の前に電池缶１３の内部に注入する。電解液の注入方法は、電池蓋２０を解放した状態にて電極群に直接添加する方法、又は電池蓋２０に設置した注入口から添加する方法がある。正極１０および負極１２のそれぞれに電流引き出し用の正極集電タブ１４、負極集電タブ１５をスポット溶接または超音波溶接により形成する。正極集電タブ１４、負極集電タブ１５は、長方形の形状をした正極集電体、負極集電板とそれぞれ同じ材質の金属箔からできており、正極１０および負極１２から電流を取り出すために設置する部材である。本発明は自動車などの移動体用リチウム二次電池に適用することができ、これらは、大電流を流すことが要求されるため、自動車などの移動体用リチウム二次電池に適用する場合複数のタブを設ける必要がある。 The electrode group is housed in the battery can 13, the negative electrode current collecting tab 15 is connected to the inner wall of the battery can 13, and the positive electrode current collecting tab 14 is connected to the bottom surface of the battery lid 20. The electrolyte is injected into the battery can 13 before the battery is sealed. As a method for injecting the electrolyte, there are a method of adding directly to the electrode group in a state where the battery cover 20 is released, or a method of adding from an injection port installed in the battery cover 20. A positive current collecting tab 14 and a negative current collecting tab 15 for drawing current are formed on each of the positive electrode 10 and the negative electrode 12 by spot welding or ultrasonic welding. The positive electrode current collecting tab 14 and the negative electrode current collecting tab 15 are made of a metal foil of the same material as the positive electrode current collector and the negative electrode current collector plate each having a rectangular shape, and for taking out current from the positive electrode 10 and the negative electrode 12. It is a member to install. The present invention can be applied to a lithium secondary battery for a mobile object such as an automobile, and since these are required to pass a large current, a plurality of lithium secondary batteries for a mobile object such as an automobile are used. It is necessary to provide a tab.
　その後、電池蓋２０を電池缶１３に密着させ、電池全体を密閉する。電解液の注入口がある場合は、それも密封する。電池を密閉する方法には、溶接、かしめ等公知の技術がある。なお、電池蓋２０には電池内の圧力が上昇すると開裂して電池内部の圧力を逃がす逃し弁が設けられている。 Thereafter, the battery lid 20 is brought into close contact with the battery can 13 and the whole battery is sealed. If there is an electrolyte inlet, seal it as well. As a method for sealing the battery, there are known techniques such as welding and caulking. The battery lid 20 is provided with a relief valve that is opened when the pressure inside the battery rises and releases the pressure inside the battery.
　本発明の一実施形態に係るリチウムイオン二次電池は、例えば、下記のような負極と正極とをセパレータを介して対向して配置し、電解質を注入することによって製造することができる。本発明の一実施形態に係るリチウムイオン電池の構造は特に限定されないが、通常、正極及び負極とそれらを隔てるセパレータとを捲回して捲回式電極群にするか、又は正極、負極及びセパレータを積層させて積層型の電極群とすることができる。 The lithium ion secondary battery according to an embodiment of the present invention can be manufactured by, for example, disposing the following negative electrode and positive electrode facing each other via a separator and injecting an electrolyte. The structure of the lithium ion battery according to an embodiment of the present invention is not particularly limited. Usually, the positive electrode and the negative electrode and the separator separating them are wound into a wound electrode group, or the positive electrode, the negative electrode, and the separator are combined. A stacked electrode group can be formed by stacking.
＜負極＞
　本発明の一実施形態に係る負極材は、負極活物質である炭素のエッジ部分の存在するＣ＝Ｏ、Ｃ－ＯＨ、－ＣＯＯＨ結合等の表面官能基とホウ素を含有する化合物が反応することで、負極活物質表面に固定化、つまり負極活物質とホウ素を含有する化合物が共有結合化することが可能になる。この負極活物質の表面に存在する表面官能基は電池反応で電解液と不可逆に反応することで、ＳＥＩ被膜という表面被膜を形成する。この表面被膜の生成のためには、電荷が消費され、電池の容量低下の一因になる。さらには、電池の経時劣化を抑制するためには、電解液との経時的な反応を抑制するような被膜を形成することで長寿命化が可能になると考えられる。 <Negative electrode>
In the negative electrode material according to an embodiment of the present invention, a boron-containing compound reacts with a surface functional group such as a C═O, C—OH, and —COOH bond in which a carbon edge portion as a negative electrode active material exists. Thus, the negative electrode active material can be immobilized on the surface, that is, the negative electrode active material and the boron-containing compound can be covalently bonded. The surface functional group present on the surface of the negative electrode active material reacts irreversibly with the electrolytic solution in a battery reaction, thereby forming a surface film called an SEI film. The generation of the surface coating consumes electric charge and contributes to a decrease in battery capacity. Furthermore, in order to suppress the deterioration of the battery over time, it is considered that the lifetime can be extended by forming a film that suppresses the reaction with the electrolyte over time.
　本発明の一実施形態における負極材にリチウム二次電池を作製すると、Ｂ－Ｏ結合をもつホウ素化合物を負極活物質表面の一部または全部に固定化することで、電池の経時劣化を抑制し、寿命向上することを見出した。負極活物質表面の一部または全部に化合物を固定化することで、電解液への溶出の懸念が低下するとともに、正極の特性低下も抑制することが可能になり、電池特性向上に寄与したものと考えられる。 When a lithium secondary battery is manufactured as a negative electrode material according to an embodiment of the present invention, a boron compound having a BO bond is immobilized on a part or all of the surface of the negative electrode active material, thereby suppressing deterioration with time of the battery. , Found to improve life. By immobilizing the compound on part or all of the surface of the negative electrode active material, it is possible to reduce the concern of elution into the electrolyte and to suppress the deterioration of the characteristics of the positive electrode, contributing to the improvement of battery characteristics. it is conceivable that.
　本発明の一実施形態における負極活物質の原料は、表面官能基を有する物質であれば用いることができる。つまり、Ｘ線光電子分光法等で、材料を分析すると、Ｏ原子由来のピークを検出できる材料であれば用いることができる。具体的には、天然黒鉛、石油コークスや石炭ピッチコークス等から得られる易黒鉛化材料を２５００℃以上の高温で処理したもの、メソフェーズカーボンあるいは、非晶質炭素、黒鉛の表面に非晶質炭素を被覆したもの、天然あるいは人造黒鉛表面を機械的処理により表面の結晶性を低下させた炭素材、高分子など有機物を炭素表面に被覆・吸着した材料、炭素繊維、リチウム金属、リチウムと合金化する金属、シリコンあるいは炭素粒子表面に金属を担持した材料が用いられる。金属を担持した炭素材として、例えば、リチウム、アルミニウム、スズ、ケイ素、インジウム、ガリウム、マグネシウムより選ばれた金属あるいは合金が挙げられる。また上記金属または金属の酸化物を負極活物質として利用できる。これら負極活物質の候補の内、一種単独または二種以上混合させても用いることができる。 The raw material of the negative electrode active material in one embodiment of the present invention can be used as long as it has a surface functional group. That is, if a material is analyzed by X-ray photoelectron spectroscopy or the like, any material that can detect a peak derived from an O atom can be used. Specifically, graphitized materials obtained from natural graphite, petroleum coke, coal pitch coke, etc., processed at a high temperature of 2500 ° C. or higher, mesophase carbon, amorphous carbon, or amorphous carbon on the surface of graphite Coated with carbon, natural or artificial graphite surface, carbon material whose surface crystallinity has been lowered by mechanical treatment, material coated and adsorbed with organic matter such as polymer, carbon fiber, lithium metal, alloyed with lithium Metal, silicon, or a material having a metal supported on the surface of carbon particles is used. Examples of the carbon material carrying a metal include a metal or an alloy selected from lithium, aluminum, tin, silicon, indium, gallium, and magnesium. Moreover, the said metal or metal oxide can be utilized as a negative electrode active material. Of these negative electrode active material candidates, one kind can be used alone, or two or more kinds can be used in combination.
　１価あるいは２価のアルカリ金属（Ｍ）とアルコール（Ｒ－ＯＨ）との反応により生成するＲ－ＯＭとホウ酸アルキル（Ｂ－(ＯＲ)3）とを反応させ、ＭＢ(Ｏ－Ｒ)4を含む化合物が得られる。Ｍが１価のアルカリ金属の場合、化学反応式の中間体として単離できる。Ｍが２価のアルカリ金属、例えば、Ｃａイオンの場合、電荷バランスの整合をとるため会合対が生成するものと考えられるが、溶液中では溶媒和する。 MB (OR) is produced by reacting R-OM produced by the reaction of monovalent or divalent alkali metal (M) with alcohol (R—OH) and alkyl borate (B— (OR) 3 ). A compound containing 4 is obtained. When M is a monovalent alkali metal, it can be isolated as an intermediate in the chemical reaction formula. When M is a divalent alkali metal, such as Ca ion, it is considered that an association pair is formed to match the charge balance, but solvates in the solution.
　Ｒは有機基である。Ｒが直鎖の場合、メチル基、エチル基、ブチル基、プロピル基などの一般式ＣnＨm（ただし、ｍ＝２ｎ＋１、ｎは１以上の整数）などが挙げられる。Ｒの水素について、フッ素、塩素、臭素等のハロゲン元素で置換してもよい。また、イソプロピル基等の分岐型のアルキル基等を用いても良い。Ｒが環状の場合、フェノール基などの一般式ＣnＨm（ただし、ｍ＝ｎ－１、ｎは４以上の整数）などが挙げられる。ｎ＝３以下の環状化合物は非常に不安定なので、ｎは４以上の整数であることが望ましい。 R is an organic group. When R is a straight chain, general formula C n H m (where m = 2n + 1, n is an integer of 1 or more) such as a methyl group, an ethyl group, a butyl group, and a propyl group. The hydrogen of R may be substituted with a halogen element such as fluorine, chlorine or bromine. A branched alkyl group such as an isopropyl group may also be used. When R is cyclic, a general formula C n H m such as a phenol group (where m = n−1, n is an integer of 4 or more) and the like can be mentioned. Since cyclic compounds with n = 3 or less are very unstable, n is preferably an integer of 4 or more.
　この得られたＭＢ(Ｏ－Ｒ)4と負極活物質の表面官能基とをアルコール中あるいはアセトニトリル、ジメチルスルホキシド等のより極性の高い溶媒中で撹拌し反応させることで、ホウ素およびアルカリ金属を含有した被膜剤が負極活物質の表面に形成された負極材を得ることができる。反応後の溶媒除去を容易にするという観点から、より低沸点の溶媒を用いることが望ましい。負極活物質表面での生成メカニズムおよび反応生成物については、詳細は不明であるが、炭素系の負極活物質を用いると、負極活物質の表面には、被膜剤としてＬｉ－Ｂ(－ＯＣＨ3)2－Ｃ2（活物質表面に存在する官能基由来）の形で生成するものと考えられる。表面官能基としては、－ＯＨや－ＣＯＯＨを有する材料が好適であると考えられる。化合物としてＭＢ(Ｏ－Ｒ)4のみでも良いが、ＭＢ(Ｏ－Ｒ)4以外のものが含まれていても良い。 The obtained MB (OR) 4 and the surface functional group of the negative electrode active material are stirred and reacted in a more polar solvent such as alcohol or acetonitrile or dimethyl sulfoxide, thereby containing boron and an alkali metal. A negative electrode material in which the coated film agent is formed on the surface of the negative electrode active material can be obtained. From the viewpoint of facilitating solvent removal after the reaction, it is desirable to use a solvent having a lower boiling point. The details of the formation mechanism and reaction product on the surface of the negative electrode active material are unknown, but when a carbon-based negative electrode active material is used, Li—B (—OCH 3 ) 2 -C 2 (derived from a functional group present on the surface of the active material). As the surface functional group, a material having —OH or —COOH is considered suitable. MB as the compound (O-R) 4 only may be but, MB (O-R) may contain 4 else.
　また、反応条件として、Ｒ－ＯＭとＢ－(ＯＲ)3、ＭＢ(Ｏ－Ｒ)4は水分と反応しやすい物質であるので、ＡｒあるいはＮ2等の不活性雰囲気化で反応させることが望ましいが、大気中であっても、反応収率が幾分低下するのみで、その後の負極活物質との撹拌時間、加熱等の工程条件を選定することでも収率を維持することが可能である。 As reaction conditions, R-OM, B- (OR) 3 , and MB (O—R) 4 are substances that easily react with moisture, so that they can be reacted in an inert atmosphere such as Ar or N 2. Although it is desirable, even in the atmosphere, the reaction yield is only slightly reduced, and it is possible to maintain the yield by selecting process conditions such as subsequent stirring time with the negative electrode active material and heating. is there.
　ホウ素化合物として具体的には、ホウ酸トリメチル（Ｂ(ＯＣＨ3)3）、ホウ酸トリエチル（Ｂ(ＯＣＨ2ＣＨ3)3）、ホウ酸トリプロピル（Ｂ(ＯＣＨ2ＣＨ2ＣＨ3)3）などのホウ酸アルキルなどが挙げられる。沸点が低く、除去しやすいという観点で、アルキル基の短いホウ酸トリメチルを用いることが望ましい。 Specific examples of boron compounds include trimethyl borate (B (OCH 3 ) 3 ), triethyl borate (B (OCH 2 CH 3 ) 3 ), and tripropyl borate (B (OCH 2 CH 2 CH 3 ) 3 ). And alkyl borate. From the viewpoint of low boiling point and easy removal, it is desirable to use trimethyl borate having a short alkyl group.
　負極１２は、例えば上記の負極材を用い、カルボキシメチルセルロースおよびスチレンブタジエン共重合体等のバインダと混合して塗布プレスし、電極を作製する。負極合剤層の厚さは５０～２００μｍとするのが望ましい。負極１２の場合は、負極集電体として厚さ７～２０μｍの銅箔を用いることが望ましい。このように、負極１２を作成する前に負極活物質に被膜剤を事前に固定しておくことで電池の高容量化を達成できる。 For the negative electrode 12, for example, the above negative electrode material is used, mixed with a binder such as carboxymethyl cellulose and a styrene butadiene copolymer, and applied and pressed to produce an electrode. The thickness of the negative electrode mixture layer is preferably 50 to 200 μm. In the case of the negative electrode 12, it is desirable to use a copper foil having a thickness of 7 to 20 μm as the negative electrode current collector. Thus, the battery capacity can be increased by fixing the coating agent to the negative electrode active material in advance before forming the negative electrode 12.
　カルボキシメチルセルロースやスチレンブタジエン共重合体等の分散材・バインダは、合計で３wt％程度とすることが望ましい。バインダ成分が多くなると内部抵抗値の増加や電池容量の低下につながる。また、バインダ成分が少なすぎると、電極剥離の作製が困難になったり、電池の保存、サイクル寿命の低下を招いたりする可能性がある。また、有機系バインダを用いる場合も３－６wt％程度にすることが望ましいが、電池の保存、サイクル寿命の試験結果を基に、配合比を決定することがより望ましい。 It is desirable that the total amount of the dispersing agent / binder such as carboxymethyl cellulose and styrene butadiene copolymer is about 3 wt%. When the binder component increases, the internal resistance value increases and the battery capacity decreases. Moreover, when there are too few binder components, preparation of electrode peeling may become difficult, storage of a battery, and the fall of a cycle life may be caused. In the case of using an organic binder, it is desirable to set it to about 3-6 wt%, but it is more desirable to determine the blending ratio based on the results of battery storage and cycle life tests.
＜正極＞
　正極１０は、正極活物質、導電剤、バインダ、及び正極集電体から構成される。本発明の一実施形態における負極活物質をリチウムイオン二次電池に用いる場合は、リチウムを可逆的に吸蔵放出する正極活物質として、コバルト酸リチウム（ＬｉＣｏＯ2）、ニッケル酸リチウム（ＬｉＮｉＯ2）などの層状化合物、またはこれらの一種以上を遷移金属で置換したもの、あるいはマンガン酸リチウムＬｉ1+xＭｎ2-xＯ4（ただしｘ＝０～０.３３）、Ｌｉ1+xＭｎ2-x-yＭyＯ4（ただし、ＭはＮｉ、Ｃｏ、Ｆｅ、Ｃｕ、Ａｌ、Ｍｇより選ばれた少なくとも一種の金属を含み、ｘ＝０～０.３３、ｙ＝０～１.０、２－ｘ－ｙ＞０）、ＬｉＭｎＯ4、ＬｉＭｎ2Ｏ4、ＬｉＭｎＯ2、ＬｉＭｎ2-xＭxＯ4（ただし、ＭはＮｉ、Ｃｏ、Ｆｅ、Ｃｕ、Ａｌ、Ｍｇより選ばれた少なくとも一種の金属を含み、ｘ＝０.０１～０.１）、Ｌｉ2Ｍｎ3ＭＯ8（ただし、ＭはＮｉ、Ｃｏ、Ｆｅ、Ｃｕ、Ａｌ、Ｍｇより選ばれた少なくとも一種の金属を含む）、銅－Ｌｉ酸化物（ＬｉＣｕＯ2）、ジスルフィド化合物、Ｆｅ2(ＭｏＯ4)3などを含む混合物、あるいはポロアニリン、ポリピロール、ポリチオフェンなどの一種または二種以上の混合物を用いることができる。 <Positive electrode>
The positive electrode 10 includes a positive electrode active material, a conductive agent, a binder, and a positive electrode current collector. When the negative electrode active material in one embodiment of the present invention is used in a lithium ion secondary battery, as a positive electrode active material that reversibly absorbs and releases lithium, lithium cobaltate (LiCoO 2 ), lithium nickelate (LiNiO 2 ), etc. Or a compound obtained by replacing one or more of these with a transition metal, or lithium manganate Li 1 + x Mn 2-x O 4 (where x = 0 to 0.33), Li 1 + x Mn 2-xy MyO 4 (wherein M includes at least one metal selected from Ni, Co, Fe, Cu, Al and Mg, and x = 0 to 0.33, y = 0 to 1.0, 2-x -Y> 0), LiMnO 4 , LiMn 2 O 4 , LiMnO 2 , LiMn 2−x M x O 4 (where M is at least one metal selected from Ni, Co, Fe, Cu, Al, Mg) X = 0.01-0.1), L i 2 Mn 3 MO 8 (wherein M includes at least one metal selected from Ni, Co, Fe, Cu, Al and Mg), copper-Li oxide (LiCuO 2 ), disulfide compound, Fe 2 ( A mixture containing MoO 4 ) 3 or the like, or one or a mixture of two or more of polyaniline, polypyrrole, polythiophene and the like can be used.
　上記の正極活物質を炭素材料粉末の導電剤、ポリフッ化ビニリデン（ＰＶＤＦ）等のバインダとともに混合しスラリーを作製する。上記正極活物質に対する上記導電剤の混合比は、５～２０wt％が好ましい。このとき、上記の正極活物質の粉末粒子がスラリー中で均一に分散するように、回転翼のような撹拌手段を備えた混合機を用いて十分に混錬する。 The above positive electrode active material is mixed with a carbon material powder conductive agent and a binder such as polyvinylidene fluoride (PVDF) to prepare a slurry. The mixing ratio of the conductive agent to the positive electrode active material is preferably 5 to 20 wt%. At this time, the mixture is sufficiently kneaded using a mixer equipped with stirring means such as a rotary blade so that the powder particles of the positive electrode active material are uniformly dispersed in the slurry.
　十分に混合したスラリーは、例えばロール転写式の塗布機などによって厚さ１５～２５μｍのアルミ箔からなる正極集電体上に両面塗布する。両面塗布した後、プレス乾燥することよって正極１０とした。正極集電体上に塗布された正極合剤層の厚さは５０～２５０μｍとするのが望ましい。 The sufficiently mixed slurry is applied on both sides onto a positive electrode current collector made of aluminum foil having a thickness of 15 to 25 μm, for example, by a roll transfer type coating machine. After coating on both sides, a positive electrode 10 was obtained by press drying. The thickness of the positive electrode mixture layer applied on the positive electrode current collector is preferably 50 to 250 μm.
＜電解質＞
　非水溶媒としては、エチレンカーボネート、プロピレンカーボネート、ガンマブチロラクトン、ジメチルカーボネート、エチルメチルカーボネート、ジエチルカーボネートが挙げられる。また、これら溶媒については、フッ素置換体などのハロゲン化物や硫黄元素で置換したものを用いてもよい。これら溶媒は、単独で用いても二種以上混合して用いてもよい。なお、二種類以上の溶媒を用いる場合は、環状カーボネートや環状ラクトンのような粘度の大きい溶媒と、鎖状カーボネートや鎖状エステルのような粘度の小さい溶媒との混合溶媒系を用いるのが好ましい。 <Electrolyte>
Examples of the non-aqueous solvent include ethylene carbonate, propylene carbonate, gamma butyrolactone, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate. Moreover, about these solvents, you may use what substituted with halides and sulfur elements, such as a fluorine-substitution thing. These solvents may be used alone or in combination of two or more. When two or more kinds of solvents are used, it is preferable to use a mixed solvent system of a solvent having a high viscosity such as cyclic carbonate or cyclic lactone and a solvent having a low viscosity such as chain carbonate or chain ester. .
　リチウム塩としては、ＬｉＰＦ6、ＬｉＢＦ4、ＬｉＣｌＯ4、ＬｉＡｓＦ6、ＬｉＣＦ3ＳＯ2、Ｌｉ(ＣＦ3ＳＯ2)2Ｎ、Ｌｉ(Ｃ2Ｆ5ＳＯ2)Ｎ、等のリチウム塩を用いることができる。これらリチウム塩は、単独で用いても、二種以上混合して用いてもよい。電解液としては、エチレンカーボネートやプロピレンカーボネート、ジメチルカーボネート等の溶媒に電解質としてＬｉＰＦ6、ＬｉＢＦ4を溶解させたものを用いることが望ましい。電解質濃度としては、０.６～１.５mol／Ｌの間とするのが望ましい。 Lithium salt such as LiPF 6 , LiBF 4 , LiClO 4 , LiAsF 6 , LiCF 3 SO 2 , Li (CF 3 SO 2 ) 2 N, Li (C 2 F 5 SO 2 ) N, etc. should be used as the lithium salt. Can do. These lithium salts may be used alone or in combination of two or more. As the electrolytic solution, it is desirable to use a solution of LiPF 6 or LiBF 4 as an electrolyte in a solvent such as ethylene carbonate, propylene carbonate, or dimethyl carbonate. The electrolyte concentration is preferably between 0.6 and 1.5 mol / L.
　ビニレンカーボネートやカルボン酸無水基を有する化合物、プロパンサルトン等硫黄元素を有する化合物やホウ素を有する化合物を溶媒、溶質以外の第３成分として電解液に混合させることも可能である。混合する場合も溶媒、溶質以外に二種以上の化合物を混合させることも可能である。これら、化合物の添加目的は、負極活物質表面での還元分解の抑制以外にも、正極活物質からのＭｎ溶出抑制や、電解液のイオン導電性を向上、電解液の不燃、難燃化等目的に応じ選択する。さらに、電池の諸特性向上のため、例えば、ビニレンカーボネート・プロパンサルトン等の負極活物質の表面に被膜を形成する被膜剤、シクロヘキシルベンゼン等の過充電防止添加剤、リン酸系やハロゲン置換により難燃性を付与させる添加剤、自己消化性添加剤、電極・セパレータ濡れ性改善添加剤等を、それぞれの目的に応じて添加してもよい。 It is also possible to mix vinylene carbonate, a compound having a carboxylic acid anhydride group, a compound having a sulfur element such as propane sultone, or a compound having boron as a third component other than a solvent and a solute in the electrolytic solution. When mixing, it is also possible to mix two or more compounds in addition to the solvent and solute. The purpose of adding these compounds is not only to suppress reductive decomposition on the surface of the negative electrode active material, but also to suppress Mn elution from the positive electrode active material, improve the ionic conductivity of the electrolyte, make the electrolyte non-flammable, flame retardant, etc. Select according to purpose. Furthermore, in order to improve various characteristics of the battery, for example, a coating agent that forms a coating on the surface of a negative electrode active material such as vinylene carbonate / propane sultone, an overcharge prevention additive such as cyclohexylbenzene, phosphoric acid type or halogen substitution Additives that impart flame retardancy, self-extinguishing additives, electrode / separator wettability improving additives, and the like may be added according to their respective purposes.
＜セパレータ＞
　正極１０および負極１２の直接接触による短絡防止を目的にセパレータ１１を用いるが、このセパレータ１１には、ポリエチレン、ポリプロピレン、アラミド樹脂等の微多孔質の高分子フィルムやこの高分子フィルムにアルミナ粒子等の耐熱性物質を表面に被覆した膜等も使用することができる。 <Separator>
A separator 11 is used for the purpose of preventing a short circuit due to direct contact between the positive electrode 10 and the negative electrode 12, and the separator 11 includes a microporous polymer film such as polyethylene, polypropylene, and aramid resin, and alumina particles and the like on this polymer film. A film having a surface coated with a heat-resistant substance can be used.
　以下、本発明の実施例、および比較例によって本発明をさらに具体例を挙げ説明する。 Hereinafter, the present invention will be further described with reference to examples and comparative examples.
　正極活物質には、平均粒径１０μｍ、比表面積１.５ｍ2／ｇのＬｉ1.02Ｍｎ1.98Ａｌ0.02Ｏ4を用いた。正極活物質８５重量％に、塊状黒鉛とアセチレンブラックを９：２に混合したものを導電剤とし、結着剤として予め５重量％ＰＶＤＦに調整されたＮＭＰ溶液に導電剤を分散させてスラリーにした。正極活物質、導電剤、ＰＶＤＦの混合比は、重量比で８５：１０：５にした。 As the positive electrode active material, Li 1.02 Mn 1.98 Al 0.02 O 4 having an average particle diameter of 10 μm and a specific surface area of 1.5 m 2 / g was used. A mixture of 9: 2 of massive graphite and acetylene black mixed with 85% by weight of the positive electrode active material is used as a conductive agent, and the conductive agent is dispersed in an NMP solution that has been previously adjusted to 5% by weight PVDF as a binder. did. The mixing ratio of the positive electrode active material, the conductive agent, and PVDF was 85: 10: 5 by weight.
　このスラリーを厚さ２０μｍのアルミニウム箔（正極集電体）にできるだけ均一かつ均等に塗布した。塗布後、８０℃の温度で乾燥し、同じ手順でアルミニウム箔の両面に塗布乾燥を行った。その後ロールプレス機により圧縮成形し、塗布幅５.４cm、塗布長さ５０cmとなるよう切断し、電流を取り出すためのアルミニウム箔製のリード片を溶接し正極１０を作製した。 The slurry was applied as uniformly and evenly as possible to an aluminum foil (positive electrode current collector) having a thickness of 20 μm. After the application, the film was dried at a temperature of 80 ° C., and applied and dried on both sides of the aluminum foil in the same procedure. Thereafter, it was compression-molded by a roll press machine, cut to a coating width of 5.4 cm and a coating length of 50 cm, and an aluminum foil lead piece for taking out the current was welded to produce the positive electrode 10.
　負極活物質にはＸ線回折測定で得られた面間隔が０.３６８nm、平均粒径が２０μｍ、比表面積が５ｍ2／ｇの天然黒鉛を用いた。先ず、リチウム金属とメタノールとの反応により生成するメタノールアルコキサイドを得、次いでホウ酸トリメチルと反応させ、ＬｉＢ(Ｏ－ＣＨ3)4を合成した。この得られたＬｉＢ(Ｏ－ＣＨ3)4と負極活物質の表面官能基とを反応させることで、ホウ素およびアルカリ金属を含有した負極材が得られた。得られた負極材をＸ線光電子分光分析で測定すると、ホウ素に基づく１９２－１９３eVにホウ素原子を確認できた。また、Ｌｉ由来のピークを５５－５６eVに確認することができた。このホウ素由来のピークとリチウム由来のピークのピーク強度比から求められる元素比率は１：１であった。 As the negative electrode active material, natural graphite having an interplanar spacing of 0.368 nm, an average particle diameter of 20 μm, and a specific surface area of 5 m 2 / g obtained by X-ray diffraction measurement was used. First, methanol alkoxide formed by reaction of lithium metal and methanol was obtained, and then reacted with trimethyl borate to synthesize LiB (O—CH 3 ) 4 . By reacting the obtained LiB (O—CH 3 ) 4 with the surface functional group of the negative electrode active material, a negative electrode material containing boron and an alkali metal was obtained. When the obtained negative electrode material was measured by X-ray photoelectron spectroscopic analysis, boron atoms were confirmed at 192 to 193 eV based on boron. In addition, a peak derived from Li could be confirmed at 55 to 56 eV. The element ratio determined from the peak intensity ratio of the peak derived from boron and the peak derived from lithium was 1: 1.
　負極材とカルボキシメチルセルロースの水分散液と充分に混合し、スチレンブタジエン共重合体の水分散液を分散させて負極スラリーとした。負極材、カルボキシメチルセルロース、スチレンブタジエンの混合比は、重量比で９８：１：１にした。このスラリーを厚さ１０μｍの圧延銅箔（負極集電体）に実質的に均一塗布した。 The negative electrode material and an aqueous dispersion of carboxymethyl cellulose were sufficiently mixed, and the aqueous dispersion of styrene-butadiene copolymer was dispersed to obtain a negative electrode slurry. The mixing ratio of the negative electrode material, carboxymethyl cellulose, and styrene butadiene was 98: 1: 1 by weight. This slurry was applied substantially uniformly to a rolled copper foil (negative electrode current collector) having a thickness of 10 μm.
　正極１０と同様の手順で圧延銅箔の両面に塗付乾燥を行った。その後ロールプレス機により圧縮成形し、塗布幅５.６cm、塗布長さ５４cmとなるよう切断し、銅箔製のリード片を溶接し負極１２を作製した。 The coating and drying were performed on both sides of the rolled copper foil in the same procedure as the positive electrode 10. Thereafter, it was compression-molded by a roll press machine, cut so as to have a coating width of 5.6 cm and a coating length of 54 cm, and a lead piece made of copper foil was welded to prepare the negative electrode 12.
　作製した正極１０と負極１２を用いて図１に示す円筒型の電池１を作製した。図１に示す正極１と負極２とし、それぞれ電流引き出し用のタブ部の正極リード７、負極リード５を超音波溶接により形成する。タブ部の正極リード７、負極リード５は、長方形の形状をした集電体とそれぞれ同じ材質の金属箔からできており、電極から電流を取り出すために設置する部材である。タブ付けされた正極１及び負極２の間にポリエチレンの単層膜であるセパレータ１１を挟んで重ね、これを、図１に示すように、円筒状（螺旋状）に捲いて電極群とし、円筒状容器の電池缶１３に収納した。電極群を電池缶１３に収納した後、電池缶１３内に電解液を注入し、ガスケットで密封させた。　
　電解液には、エチレンカーボネート（ＥＣ）とエチルメチルカーボネート（ＥＭＣ）を重量比でＥＣ：ＥＭＣ＝１：２の割合で混合した混合溶液に電解質としてＬｉＰＦ6を濃度が１.０mol／Ｌになるように溶解させた。さらに、ビニレンカーボネートをこの混合溶液の重量に対して１wt％になるように混合させた。このように作製した電解液を正極端子が取り付けられた密閉用の電池蓋２０をガスケット１８を介して電池缶１３に注液し、かしめにより密閉して、径１８mm、長さ６５０mmの円筒型の電池１とした。 A cylindrical battery 1 shown in FIG. 1 was produced using the produced positive electrode 10 and negative electrode 12. A positive electrode 1 and a negative electrode 2 shown in FIG. 1 are formed, and a positive electrode lead 7 and a negative electrode lead 5 of a tab portion for drawing out current are formed by ultrasonic welding. The positive electrode lead 7 and the negative electrode lead 5 in the tab portion are made of metal foils of the same material as the current collector having a rectangular shape, and are members installed to take out current from the electrodes. A separator 11, which is a polyethylene single layer film, is sandwiched between the tabbed positive electrode 1 and negative electrode 2, and this is rolled into a cylindrical shape (spiral) as shown in FIG. The battery can 13 was housed in a cylindrical container. After the electrode group was housed in the battery can 13, an electrolytic solution was injected into the battery can 13 and sealed with a gasket.
In the electrolyte, LiPF 6 concentration becomes 1.0 mol / L as an electrolyte in a mixed solution in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed at a weight ratio of EC: EMC = 1: 2. So that it was dissolved. Furthermore, vinylene carbonate was mixed so that it might become 1 wt% with respect to the weight of this mixed solution. The thus-prepared electrolyte is poured into a battery can 13 through a gasket 18 and a battery lid 20 for sealing, to which a positive electrode terminal is attached, and is sealed by caulking to form a cylindrical shape having a diameter of 18 mm and a length of 650 mm. Battery 1 was obtained.
　このように作製した円筒型の電池１について、２５℃の恒温槽内で、充電電流１５０mA、電圧４.２Ｖ、５時間の定電流定電圧充電をし、放電は放電電流１５００mAで電池電圧３.０Ｖまで定電流放電した。この充電、放電プロセスを１サイクルとし、合計３サイクルした。３サイクル目の放電容量を１００％として、６０日保存試験後の１５００mA放電容量との比を算出した。この比を放電容量維持率とする。保存試験の条件は、４.２Ｖの電圧で、５０℃の恒温槽内に放置した。６０日後の電池容量の測定は、２５℃の恒温槽内に１０時間以上放置し、除熱してから試験開始した。 The cylindrical battery 1 manufactured in this way was charged in a constant temperature bath at 25 ° C. with a charging current of 150 mA, a voltage of 4.2 V, and a constant current and a constant voltage of 5 hours, and discharging was performed at a discharging current of 1500 mA and a battery voltage of 3. A constant current was discharged to 0V. This charging / discharging process was defined as one cycle, for a total of 3 cycles. The discharge capacity at the third cycle was defined as 100%, and the ratio with the 1500 mA discharge capacity after the 60-day storage test was calculated. This ratio is defined as a discharge capacity maintenance rate. The storage test was conducted at a voltage of 4.2 V in a constant temperature bath at 50 ° C. The measurement of the battery capacity after 60 days was left in a constant temperature bath at 25 ° C. for 10 hours or more, and the test was started after removing heat.
　負極活物質の反応物質にホウ酸トリメチルの代わりにホウ酸トリエチルを用いた以外は、実施例１と同様にして円筒型電池を作製して試験した。 A cylindrical battery was prepared and tested in the same manner as in Example 1 except that triethyl borate was used instead of trimethyl borate as the reactant of the negative electrode active material.
〔比較例１〕
　ホウ素処理をしていない無垢な天然黒鉛を用いた以外は、実施例１と同様にして円筒型電池を作製して電池試験した。 [Comparative Example 1]
A cylindrical battery was produced and tested in the same manner as in Example 1 except that solid natural graphite not subjected to boron treatment was used.
〔比較例２〕
　電解液にＬｉＢ(Ｏ－ＣＨ3)4を１wt％の濃度で溶解させた以外は、比較例１と同様に円筒型電池を作製して電池試験した。 [Comparative Example 2]
A cylindrical battery was prepared and tested in the same manner as in Comparative Example 1 except that LiB (O—CH 3 ) 4 was dissolved in the electrolyte at a concentration of 1 wt%.
〔比較例３〕
　電解液にＬｉＢ(Ｏ－ＣＨ3)4を２wt％の濃度で溶解させた以外は、比較例１と同様に円筒型電池を作製して電池試験した。 [Comparative Example 3]
A cylindrical battery was prepared and tested in the same manner as in Comparative Example 1 except that LiB (O—CH 3 ) 4 was dissolved in the electrolyte at a concentration of 2 wt%.
　表１には、上述の各電池試験の結果として、６０日後の高温保存特性を示す。 Table 1 shows the high temperature storage characteristics after 60 days as a result of each of the battery tests described above.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
＜考察＞
　先ず、ホウ素処理をしていない無垢な天然黒鉛を用いた場合（比較例１）を基準にして、実施例１のホウ酸トリメチルを出発原料の一つにした負極活物質を用いて、電池試験をしたところ、６０日後の放電容量は５.２％向上していた。負極活物質表面にホウ素・リチウムを含有する被膜を形成したため、負極活物質界面での電解液の分解による性能低下を抑制することで、電池経時劣化を抑制したものと考えられる。 <Discussion>
First, on the basis of the case of using pure natural graphite not subjected to boron treatment (Comparative Example 1), a battery test was conducted using a negative electrode active material in which trimethyl borate of Example 1 was used as one of starting materials. As a result, the discharge capacity after 60 days was improved by 5.2%. Since a film containing boron / lithium is formed on the surface of the negative electrode active material, it is considered that the deterioration with time of the battery is suppressed by suppressing the performance degradation due to the decomposition of the electrolyte solution at the negative electrode active material interface.
　実施例２に記載のように、ホウ酸トリエチルを出発原料にした場合は、６０日後保存後の容量は、比較例１と比較して４.３％向上していた。ホウ酸基に結合するアルキルが変化しても、容量向上することが判った。 As described in Example 2, when triethyl borate was used as a starting material, the capacity after storage after 60 days was improved by 4.3% as compared with Comparative Example 1. It was found that the capacity was improved even when the alkyl bonded to the boric acid group was changed.
　また、実施例１と実施例２に記載の６０日後保存試験後の電池を解体し、正極・電解液を分析したところ、ホウ素元素を検出できなかったことからもホウ素含有物質を負極活物質に固定化することで、電池寿命向上に寄与できたものと考えられる。 In addition, the batteries after the 60-day storage test described in Example 1 and Example 2 were disassembled and the positive electrode / electrolyte was analyzed. As a result, the boron-containing material was used as the negative electrode active material because boron element was not detected. By fixing, it is thought that it was able to contribute to the improvement of battery life.
　比較例２に記載の電解液にホウ素・リチウムを含有した物質を溶解させる方法では、比較例１と比較して、６０日後の放電容量は６.２％低下していた。本現象については、詳細なメカニズムは不明であるが、ホウ素・リチウムを含有した物質の電解液への溶解性が低く電解液粘度上昇による特性低下あるいは電解液に添加した場合は、電解液の接触する正極への悪影響も懸念されるので、それら要因が重なりあった結果であると考えられる。
本現象は、比較例２の実験結果からも支持できる結果である。 In the method of dissolving a substance containing boron / lithium in the electrolytic solution described in Comparative Example 2, compared to Comparative Example 1, the discharge capacity after 60 days was decreased by 6.2%. Although the detailed mechanism of this phenomenon is unknown, the solubility of the substance containing boron / lithium in the electrolyte is low and the characteristics of the electrolyte deteriorate due to an increase in the viscosity of the electrolyte, or when added to the electrolyte, the contact of the electrolyte Since there is a concern about the negative effect on the positive electrode, it is thought that this is a result of overlapping these factors.
This phenomenon can be supported from the experimental results of Comparative Example 2.
　以上の実施例および比較例によれば、ホウ素・リチウム・炭素・酸素を含有する化合物を負極活物質表面に固定化することによって、電池の保存特性を大幅に改善できることが判った。一方で、電解液に同様の化合物を溶解した場合、添加する化合物により、電解液の粘度上昇による、電池性能低下あるいは高濃度溶解が困難な場合があり、何れの場合も電池特性は低下することが判った。したがって、本発明によれば、従来の負極活物質を用いたリチウムイオン電池よりも経時劣化を抑制し、電池の寿命特性を顕著に向上させることができる。 According to the above Examples and Comparative Examples, it was found that the storage characteristics of the battery can be greatly improved by immobilizing a compound containing boron, lithium, carbon, and oxygen on the surface of the negative electrode active material. On the other hand, when the same compound is dissolved in the electrolytic solution, depending on the compound to be added, the battery performance may decrease due to the increase in the viscosity of the electrolytic solution or high concentration dissolution may be difficult. I understood. Therefore, according to the present invention, it is possible to suppress deterioration over time and to significantly improve the life characteristics of the battery as compared with the conventional lithium ion battery using the negative electrode active material.
１０　正極
１１　セパレータ
１２　負極
１３　電池缶
１４　正極集電タブ
１５　負極集電タブ
１６　内蓋
１７　内圧開放弁
１８　ガスケット
１９　抵抗素子
２０　電池蓋
２１　軸芯 DESCRIPTION OF SYMBOLS 10 Positive electrode 11 Separator 12 Negative electrode 13 Battery can 14 Positive electrode current collection tab 15 Negative electrode current collection tab 16 Inner cover 17 Internal pressure release valve 18 Gasket 19 Resistance element 20 Battery cover 21 Axle core

Claims (10)

  1. 　負極活物質と、
    　前記負極活物質に固定化された被覆剤と、を有するリチウムイオン二次電池用負極材であって、
    　前記被覆剤にホウ素およびアルカリ金属元素が含まれるリチウムイオン二次電池用負極材。     A negative electrode active material;
    A negative electrode material for a lithium ion secondary battery having a coating agent fixed to the negative electrode active material,
    A negative electrode material for a lithium ion secondary battery, wherein the coating agent contains boron and an alkali metal element.
  2. 　請求項１において、
    　前記負極活物質に－ＯＨまたは－ＣＯＯＨが含まれるリチウムイオン二次電池用負極材。     In claim 1,
    A negative electrode material for a lithium ion secondary battery, wherein the negative electrode active material contains -OH or -COOH.
  3. 　請求項１乃至２のいずれかにおいて、
    　前記被覆剤にＭＢ(Ｏ－Ｒ)4（Ｍは１価あるいは２価のアルカリ金属元素、Ｒは有機基）が含まれるリチウムイオン二次電池用負極材。     In any one of Claims 1 thru | or 2.
    A negative electrode material for a lithium ion secondary battery, wherein the coating agent contains MB (OR) 4 (M is a monovalent or divalent alkali metal element and R is an organic group).
  4. 　請求項１乃至３のいずれかにおいて、
    　前記負極活物質は天然黒鉛質であるリチウムイオン二次電池用負極材。     In any one of Claims 1 thru | or 3,
    The negative electrode active material for a lithium ion secondary battery, wherein the negative electrode active material is natural graphite.
  5. 　請求項１乃至４のいずれかにおいて、
    　前記被覆剤の原材料にＢ－(ＯＲ)3（Ｒは有機基）が含まれるリチウムイオン二次電池用負極材。     In any one of Claims 1 thru | or 4,
    A negative electrode material for a lithium ion secondary battery, wherein B- (OR) 3 (R is an organic group) is contained in the raw material of the coating agent.
  6. 　請求項１乃至５のいずれかのリチウムイオン二次電池用負極材を用いたリチウムイオン二次電池用負極。 A negative electrode for a lithium ion secondary battery using the negative electrode material for a lithium ion secondary battery according to any one of claims 1 to 5.
  7. 　請求項６のリチウムイオン二次電池用負極と、
    　リチウムイオン二次電池用正極と、
    　電解液と、を含むリチウムイオン二次電池。     A negative electrode for a lithium ion secondary battery according to claim 6,
    A positive electrode for a lithium ion secondary battery;
    And a lithium ion secondary battery.
  8. 　請求項７において、
    　前記リチウムイオン二次電池用正極および前記電解液にはホウ素が検出されないリチウムイオン二次電池。     In claim 7,
    A lithium ion secondary battery in which boron is not detected in the positive electrode for the lithium ion secondary battery and the electrolytic solution.
  9. 　負極活物質と、
    　前記負極活物質に固定化された被覆剤と、を有するリチウムイオン二次電池用負極材の製造方法であって、
    　前記被覆剤にホウ素およびアルカリ金属元素が含まれ、
    　前記被覆剤と前記負極活物質の表面官能基とを反応させることで前記被覆剤は前記負極活物質に固定化されるリチウムイオン二次電池用負極材の製造方法。     A negative electrode active material;
    A method for producing a negative electrode material for a lithium ion secondary battery having a coating agent fixed to the negative electrode active material,
    The coating agent contains boron and an alkali metal element,
    The method for producing a negative electrode material for a lithium ion secondary battery, wherein the coating agent is immobilized on the negative electrode active material by reacting the coating agent with a surface functional group of the negative electrode active material.
  10. 　負極活物質と、
    　前記負極活物質に固定化された被覆剤と、を有するリチウムイオン二次電池用負極材を用いたリチウムイオン二次電池用負極の製造方法であって、
    　前記被覆剤が固定化された前記負極活物質をバインダと混合してスラリーを作製する工程と、
    　前記スラリーを負極集電体に塗布する工程と、
    　前記負極集電体に塗布された前記スラリーをプレスする工程と、を含むイオン二次電池用負極の製造方法。     A negative electrode active material;
    A method of producing a negative electrode for a lithium ion secondary battery using a negative electrode material for a lithium ion secondary battery having a coating agent fixed to the negative electrode active material,
    Mixing the negative electrode active material with the coating agent immobilized thereon with a binder to produce a slurry;
    Applying the slurry to a negative electrode current collector;
    Pressing the slurry applied to the negative electrode current collector. A method for producing a negative electrode for an ion secondary battery.
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